Home › Forums › Hardware › Missing information on MPU Digital Inputs

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    • craigbealcraigbeal
      Participant
      August 13, 2024 at 1:22 pm
      Post count: 15
      #18373

      I’m looking for information about how the MPU Digital Inputs are interfaced. The datasheet provides the pin numbers, but I cannot seem to find information about the voltage range, pullup/pulldown inclusion and settings, etc.

      I am using a FlexBench 1.2 and the Simulink GPIO Read blocks, but cannot seem to get any readings into my model.

    • ConnorConnor
      Keymaster
      August 13, 2024 at 2:21 pm
      Post count: 36
      #18393

      Hi craigbeal,

      Thanks for raising this concern,

      We are currently working on this information and we will get back to you with the Digital Inputs webpage for your convenience at the earliest.

      Thanks
      Sandeep Jayabal

    • craigbealcraigbeal
      Participant
      August 19, 2024 at 3:42 pm
      Post count: 15
      #18460

      Hi Sandeep,

      I believe that most of this information was previously available via the Input/Output page. However, I still do not see any info about the GPIO pins on the MPU, which was my specific need. Thanks in advance.

      • ConnorConnor
        Keymaster
        August 20, 2024 at 11:27 am
        Post count: 36
        #18462

        Hi craigbeal,

        Please find the information below:

        The Digital inputs can be configured for Pull up / pull down based on requirements using the (hardware) DIP switch. It is not software configurable for FCB 1.2.

        Toggle the “MPU DI-10K-PD” for pull down configuration and “MPU DI-10K-PU” for pull up configuration. (shown in the image)

        Kindly refer to the digital input guide https://www.audesseinc.com/resources/digital-input-guide/ for additional details

        Please do let me know for any further support

        Thanks
        Sandeep Jayabal

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    • ConnorConnor
      Keymaster
      August 20, 2024 at 12:06 pm
      Post count: 36
      #18464

      Hi Craigbeal,

      In addition to the information above:

      Please find the link to the datasheet https://www.audesseinc.com/resources/datasheet/?model_sku=FlexBench+1.2&fusion-form-nonce-17520=f102ce5f7b

      In the datasheet, when the mouse pointer is hovered over each pin, the GPIO name (shown in red) pops up and its corresponding connector pins (shown in yellow box), Breakout board (shown in green box) is listed.

      Please let me know if this clarifies your query or incase otherwise please let me know.

      Thanks
      Sandeep Jayabal

      • This reply was modified 9 months, 4 weeks ago by ConnorConnor.
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    • craigbealcraigbeal
      Participant
      May 27, 2025 at 3:20 pm
      Post count: 15
      #19864

      Sorry to revive an old thread, but I think it’s most pertinent to raise the question here. After looking into this for a bit, I’ve realized that I don’t know what voltage the pull-up resistor pulls the voltage *to*. It would be really helpful if you could add more detail to the Digital Inputs page, perhaps making separate sections for the MCU and MPU units since the DIO systems are very different on each of these units.

      • AmirFAmirF
        Moderator
        May 28, 2025 at 3:54 pm
        Post count: 31
        #19874

        The pull up voltage on MPU DI will be the same as the V_BATT. So if 12V is connected to V_BATT, the pull up will be 10K ohm to 12V.
        This is the same as DI pull ups for MCU.

    • craigbealcraigbeal
      Participant
      May 28, 2025 at 3:25 pm
      Post count: 15
      #19871

      Adding a bit more information, it appears that my FlexBench MPU is pulling the pins “up” to about 1.5 volts, which is actually not enough to read the pin as high according to the following page (https://www.audesseinc.com/resources/flexcase-s/digital-input-guide/). I’ve also found that a switch that grounds MPU DI7 also drags DI8 down by a substantial percentage. I’m double-checking that none of this is related to my circuitry, but so far I haven’t found any issues.

      • AmirFAmirF
        Moderator
        May 28, 2025 at 4:02 pm
        Post count: 31
        #19875

        Where are you measuring the 1.5V on DI? Is it measuring 1.5V on the external screw terminal pin?
        Please make sure you activate only one of the Pull dip switches at any time.
        Please also note that the dip switch controls the pull for the whole MPU digital input terminal. So, all of them can be set to either pull down or pull up. In case you need different pulls on MPU DI, you should add them externally.

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      • craigbealcraigbeal
        Participant
        May 29, 2025 at 9:03 am
        Post count: 15
        #19877

        Yes, measuring 1.5V on the external screw terminal. I’ve got only the MPU DI-10K-PU switch moved to the left (the “on” position). I just disconnected all of the wires on the MPU DI pins (C3-59,60,19,20,71,72,31,32) and I still have low voltage between GND and any one of these pins. Is there anything else that could be loading the subsystem? Or is it possible that my CM4 is actually running off of this low voltage coming from the power supply? I measure 4.83 volts on the leads of the potentiometers that are being run off of the FlexBench 5 volt rail, if this is helpful. (V_batt is around 13.3 volts.)

        As an aside, I’ve attached a picture of my FlexBench board that has a bit of corrected wiring. I’m assuming this is not related, but worth mentioning.

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      • craigbealcraigbeal
        Participant
        May 29, 2025 at 9:49 am
        Post count: 15
        #19880

        A bit of additional debugging information: I shut off both DIP switches and probed the left side solder connection of them with a multi-meter. I got ~1.4 volts. I swapped CM4 boards since I had a spare; same voltage measurement. I probed when the CM4 was off as well, 0 volts on the pull-up DIP solder connection. Not sure where to trace any further back in the system. If you can provide some guidance, I’m happy to keep checking voltages and connections.

    • AmirFAmirF
      Moderator
      June 5, 2025 at 2:31 pm
      Post count: 31
      #19906

      Hi Craig,

      Sorry for my delayed answer.
      I investigated the last photo you sent and noticed a diode is missing on your board. This is the diode that is responsible for pulling up the MPU_DIs.
      So, let me know if you are comfortable with doing the rework or if you want to send the device back, and we can fix it for you.
      If you decide to do the rework, here is the simplified instruction:
      1. Please probe both pads of the diode. You need to verify that one pad has V_Batt on it, and the other pad is connected to the dip switch.
      2. The simple fix is to directly pour solder on pads and short them to have V_BATT for pull-up voltage. But remember, you will have a back-powering issue. (If VBATT is off and you put voltage on DIs, you can wake up the device)
      3. The clean, but harder fix is to populate the diode on that footprint. (MPN: BAS516,135) Anode to VBATT and Cathode to dipswitch.

      Let me know what your decision is and how I can assist you further.

      Amir

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